Potting Soil Mixture for Ferns

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Potted ferns make great indoor plants because they tolerate low-light conditions found inside. Ferns such as Japanese painted fern (Athyrium niponicum “Pictum”), which thrives in U.S. Department of Agriculture plant hardiness zones 5 through 8, leatherleaf fern (Rumohra adiantiformis), USDA zones 9 through 11, and sword fern (Nephrolepis exaltata cordifolia), USDA zones 8 through 11, grow decorative fronds that cascade over the rim of containers. Outdoors, these ferns are found growing in the wild on moist forest floors or on rotting logs. The best potting soil mixture for growing these ferns inside mimics their native soil.

Potting Soil Properties

Ferns need a porous soil mixture that provides good drainage that holds moisture near the roots. This allows excess water to drain out of the container quickly. When the soil stays wet around the roots for too long, they can begin to rot. A high amount of organic material in the potting mixture imitates the humus found in nature.

Soil for Ground Ferns

Ferns that grow in the ground in woodland settings benefit from a soil-based potting mixture. Mix together equal parts of potting soil, well-rotted compost and coarse sand. Potting soil adds weight and needs to be sterilized so there are no weed seeds or disease organisms. Compost provides nutrients and moisture to the roots of the ferns. Sand adds air pockets to the soil mixture. Do not use fine-textured sand, because it can compact the potting soil, which inhibits drainage.

Soil for Aerial Ferns

Many ferns grow on trees and rotting logs using the resources found in a soil-less growing environment. To mimic the natural growing conditions for these types of ferns, mix together 2 parts peat moss, 1 part perlite and 1 part sand. Peat moss is a popular soil replacement ingredient. It decomposes slowly and holds plenty of water. Perlite is a lightweight volcanic rock that is ground into small pieces. This element increases air space in the soil and improves drainage.

Soil for Spores

One way to propagate ferns is to shake the spores off the fronds into a tray filled with a seed-starting mixture. The mixture must be fine-textured to support the spores. Use 2 parts compost, 2 parts peat moss and 1 part vermiculite in a seed tray and mist the soil mix before spreading the spores. Medium-textured vermiculite is lightweight and contains air, which fluffs up the mixture.

About the Author

Karen Carter spent three years as a technology specialist in the public school system and her writing has appeared in the "Willapa Harbor Herald" and the "Rogue College Byline." She has an Associate of Arts from Rogue Community College with a certificate in computer information systems.